A stereo camera, in which a pair of pictures photographed by the use of two imaging means is used for calculating a distance to an object to thereby recognize the object, begins to be applied to a car-mounted system for supporting a safe traveling of a vehicle and a monitor system for detecting entrance of a suspicious person and abnormality.
In a stereo picture processing used in such systems, a triangulation technique is applied to a pair of photographed pictures spaced in position and photographed to find a distance, and a device for realization of such application generally comprises a pair of imaging means and a stereo picture processing LSI, which performs a triangulation picture processing on a pair of photographed pictures output from the imaging means. At this time, the stereo picture processing LSI performs processing to find pixel positions of a featuring point common to the mutual pictures and the number of pixels, in which the featuring points do not agree with each other in the pair of pictures among pixel information contained in the pair of pictures, thus realizing the triangulation processing. Therefore, it is ideal unless disagreement except parallax is present between the pair of pictures and it is necessary to perform regulation every imaging means so that disagreements in optical characteristic and signal characteristic are not generated. In particular, in a car-mounted situation, there is a demand for application, such as detection of a vehicle going ahead, a person, an obstacle, etc. to cope beforehand with safety, and therefore, it is necessary to surely realize distance estimation and recognition of a far distant object.
Structures, which maintain the relative, positional relationship between a pair of imaging elements in a stereo camera over a long term, are described in JP-A-11-301365 or JP-A-2003-335180.
However, the prior arts described above are one, in which a positional relationship is preserved after being mounted on the assumption that a pair of imaging elements are mounted in an exact, relative, positional relationship, and any marked contrivance is not made at the time of manufacture of a stereo camera as to how exactly left and right imaging elements are mounted in the relative relationship. Also, according to the prior arts, the positional relationship of lenses and imaging elements is first maintained in respective left and right camera parts and after regulation is made and fixation is effected so that any disagreement of the imaging elements in a direction of rotation is eliminated relative to a certain surface of a member, to which lenses and imaging elements are mounted, the camera parts are mounted to a member, which serves as a reference. However, the use of such method eliminates disagreement relative to the certain surface in the camera parts in the direction of rotation but disagreement is again generated due to machining accuracy of a mounted surface of the camera parts and a member, which serves as a reference and assembly accuracy when the camera parts are mounted to the member. Therefore, there is generated a need of decreasing such disagreement through an improvement in machining accuracy of a mount surface and assembly accuracy, so that stereo cameras involve problem of worsening in productivity and increase in cost.